The ethoxylates of various fatty alcohols and of alkylphenols are widely used in the soap and detergents industry. The majority of these ethoxylates are produced with either sodium or potassium hydroxide catalyzed processes. Although such processes are well established and have been optimized to reduce production costs, there are certain inherent constraints to using such base-catalyzed processes, including the necessity of relatively long cycle times and high ethylene oxide (“EO”) concentrations during the ethoxylation reaction. These are semibatch processes in which the starting phenol and the base are charged to a reaction vessel and the system is heated to greater than 100° C. as water is removed to shift the equilibrium from potassium hydroxide base to the potassium phenoxide base. The reactor is inerted with nitrogen so that the gas phase is maintained in a safe range after the addition of ethylene oxide. The reactors operate at relatively high ethylene oxide pressures in the range of 20 to 60 psia at the completion of ethylene oxide addition.
The current processes are true semibatch processing in which the starting alcohol or phenol and catalyst is added and the ethylene oxide is added incrementally in a process controlled by the ability to remove the heat of reaction and the ability to maintain the ethylene oxide in safe operating range. After completion of the ethylene oxide addition, the process continues until the ethylene oxide is consumed and then the catalyst is neutralized with an organic acid to give a soluble potassium or sodium salt that remains in the product. The overall cycle time is the sum of several steps which can be summarized as: starter charge, water removal, ethylene oxide addition, ethylene oxide digestion, stripping to remove any residual oxide and acid neutralization.
With the current KOH process, the amount of time in which oxide is not being added constitutes a relative large proportion of the total reactor time. For example, the starter is charged to the reactor and with a 9.5 EO nonylphenol product, this amounts to about 35% of the total material added to the reactor. Potassium hydroxide is subsequently added, usually as an aqueous solution, followed by stripping to remove water and to shift the equilibrium so that the potassium is present as the potassium phenoxide salt of the starter. These process steps have the disadvantages of occupying a significant fraction of the process time, consuming energy and producing a waste stream. After oxide addition is complete, the requirement is to drop to very low levels of residual ethylene oxide, so that the less reactive KOH requires a longer time and the product likely must be stripped to remove residual ethylene oxide.
Although the co-addition of starter and oxide is disclosed by Pazos in U.S. Pat. No. 5,777,177 and in a continuous process by Pazos and Shih (U.S. Pat. No. 5,689,012), these references fail to teach using such processes for the production of surfactants and further fail to disclose the value of an oxide addition step in which no starter is added. Other processes in which oxide and starter are added simultaneously include those described for example in U.S. Pat. No. 7,012,164; U.S. Published Patent Application No. 2003/073873; Kokai JP 06-16806; and WO 03/025045.
The patent art for the production of ethoxylates by semibatch processes includes a large number of disclosures. For example, Clement et al. in U.S. Pat. No. 6,642,423, teach ethoxylation reactions with a double metal cyanide (“DMC”) catalyst by feeding a first block of ethylene oxide followed by other blocks of propylene oxide or mixed oxides.
U.S. Pat. No. 6,821,308, issued to Combs et al. discloses oleophilic polyoxyalkylene monoethers having reduced water affinity. Combs et al. teach the alkoxylation of alcohols with DMC catalyst and exemplify propylene oxide, but not ethylene oxide. Eleveld et al., in U.S. Published Patent Application No. 2005/0014979, teach the use of DMC catalyst to prepare ethoxylated alcohols with DMC.
U.S. Published Patent Application No. 2005/0215452, in the name of Ruland et al., teaches C10-alkanol alkoxylate mixtures and processes for their preparation. Example 1 of Ruland et al. discloses the use of DMC catalyst to ethoxylate a 2-propylheptanol with 5 moles of ethylene oxide.
U.S. Published Patent Application No. 2005/0272626, in the name of Wulff et al., teaches processes for the preparation of alkoxylates of the formula RO(A)n(B)mH, in the presence of double-metal cyanide compounds. Such alkoxylates are said to be useful as emulsifiers, foam regulators, wetting agents for hard surfaces and in detergents and surfactant formulations. The alkoxylates of Wulff et al. are said to provide better cleaning efficiency with reduced odors.
Grosch et al., in WO 00/14045, teach the preparation of ethoxylates of fatty alcohols using supported DMC catalysts along with propoxylation. WO 01/04178, in the name of Walker et al. gives several examples of ethoxylation. Sherman et al. in WO 05/113640, disclose metal cutting fluids containing alkylene oxide copolymers having low pulmonary toxicity. WO 06/002807, in the name of Ostrowski et al., teaches the production of ethoxylates in a continuous reactor equipped with more than one stage and using an oxide or a mixture of oxides in the second reactor that is different from the first reactor.
Thus, there remains a need for improved surfactant production processes. New ethoxylates processes preferably should provide “drop-in products” to avoid the costs of reformulating a wide range of detergents or provide other significant improvements that would offset the reformulation costs.